On 06/08/2016 10:47 AM, Jiong Wang wrote:
As discussed on the PR
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70751,
here is the patch.
For this particular failure on arm, *arm_movsi_insn has the following
operand
constraints:
operand 0: "=rk,r,r,r,rk,m"
operand 1: "rk, I,K,j,mi,rk"
gcc won't explicitly refuse an unmatch CT_MEMORY operand (r235184) if it
comes from substituion that alternative (alt) 4 got a chance to compete
with
alt 0, and eventually be the winner as it's with rld_nregs=0 while alt 0 is
with rld_nregs=1.
I fell it's OK to give alt 4 a chance here, but we should calculate the
cost
correctly.
For alt 4, it should be treated as spill into memory, but currently lra
only
recognize a spill for pseudo register. While the spilled rtx for alt 4
is a
plus after equiv substitution.
(plus:SI (reg/f:SI 102 sfp)
(const_int 4 [0x4]))
This patch thus let lra-constraint cost spill of Non-pseudo as well and
fixed
the regression.
x86_64/aarch64/arm boostrap and regression OK.
arm bootstrapped cc1 is about 0.3% smaller in code size.
OK for trunk?
gcc/
PR rtl-optimization/70751
* lra-constraints.c (process_alt_operands): Recognize Non-pseudo
spilled into
memory.
I think the change itself is fine, but the comment could use some work.
Actually I think you just need to remove the first sentence (the one
referring to BZ70751 and r235184) and keep everything from "Suppose a
target" onward.
OK with that fix.
jeff
